1. Field of the Invention
The present invention relates to a recording art of audio signals or the like which are read out by various types of reproduction units with fidelity to the original signals, particularly to an information recording unit and method thereof to allow satisfactory recording regardless of the presence of a disturbance like vibration or a defect occurrence on a record medium.
2. Prior Art
Recently, general music or image players having a storage medium such as a disc for readout or record thereof have been produced to be widely used. Particularly, a record and reproduction system incorporating a mini-disc (called MD hereinafter) that is a magneto-optic disc is becoming popular by users. The MD is capable of record and reproduction of music data with ease in the same way as conventional audio cassettes or the like.
To simplify the following description, a record disc unit will be discussed as an example of an audio record mini-disc (MD). However, the present invention including its embodiments described later is generally applicable to various types of discs capable of record of image, data, or the like.
The MD is received in a cartridge in a manner similar to a 3.5 inch floppy disc mounted in a personal computer. The MD is capable of a maximum 74 minute record and reproduction in the same way as a CD (compact disc). The MD adopts a 44.1 kHz sampling frequency with a 16 bit quantized signal like a CD, but utilizes a data compression art called as ATRAC (Adaptive Transform Acoustic Coding) to compress recorded data by 5 to 1.
ATRAC quantizes signals by an A-D conversion like a CD, and the quantized signals are delimited with a predetermined time (the maximum is 11.6 ms) so as to be processed by Fourier transform processing to obtain about a thousand of frequency components (spectrum). The spectrum is separated into some zones based on a human auditory sense characteristic such as a minimum audible limit (each minimum audible level corresponding to each frequency) and a masking effect (a quiet sound is not audible in a loud one). The zones are efficiently marked with codes in consideration of priority thereof.
As discussed above, the record data quantity is reduced to one fifth based-on the human auditory sense characteristic so that MD is not so much inferior to CD in audibility. Such MD having a small disc diameter is presently utilized mainly in portable units as a headphone stereo.
Next, referring to the accompanied drawings, an example of a recording method for audio data or the like in relation to a conventional disc recording unit will be discussed. However, the configuration of the conventional disc recording unit will not be described since it is a most usual information recording unit (well-known unit).
FIG. 6 shows a flowchart of a recording method for audio data or the like in relation to a conventional disc recording unit.
Now, a known MD player will be discussed as one of the conventional information recording units.
As shown in FIG. 6, the information recording unit (MD player) receives a disc in its disc mounting space. According to a user's instruction to record audio data (dubbing), a CPU (not shown) which controls the MD player reads U-TOC information of the mounted mini-disc (step T1). The U-TOC information is stored in a CPU memory. Then, based on the U-TOC information, a blank area (for example, non-recorded area) is searched, and the top address n0 of the searched blank area is found out (steps T2 and T3).
Then, according to the user's instruction, a CD player (compact disc player) performs audio reproduction as an audio providing means. When the MD player starts a recording operation, the CD player outputs reproduction data on the MD.
Meanwhile, the CPU of the MD player sets the top address n0 to a blank area address variable n (step T4).
Then, the MD player converts input data to digital signals by an A-D converter, and an ATRAC encoder 22 compresses the digital signals according to a predetermined compression process to store the signals in the memory (step T5). The storing operation into the memory is continued while the CD player is supplying the data to the MD.
When a remaining data quantity in the MD player memory reaches a predetermined value A, the CPU provides a write command for a record means to record data onto the MD. Meanwhile, when a remaining data quantity in the memory has not reached the predetermined value, writing into the memory is continued (step T6).
According to the read command, a record head and a pickup search an address stored in the address variable n on the mini-disc (step T7) to record a predetermined quantity of data N stored in the memory (step T8). The recording operation is continued until the stored data quantity in the memory reaches the predetermined value.
During recording of the data N from the memory onto the disc (MD), the CPU determines whether the memory is overflowed with data supplied from the CD player due to an unsatisfactory operation such as incomplete focusing or off-tracking (steps T9 and T10).
Where a data overflow condition in the memory is detected, the CPU executes an error handling process (step T11) to forcefully terminate the recording operation. Where no data overflow in the memory is detected, the execution returns to step T7 to record the data N onto the disc again.
On the other hand, during recording the data N from the memory onto the disc (MD), when there is no unsatisfactory operation such as incomplete focusing or off-tracking to normally record the data from the memory onto the disc (MD) and step T9 has detected the normal recording completion of the data N onto the disc, a next step T12 determines whether the user has completed a dubbing operation (including storing into the memory).
After the decision of the dubbing completion, the CPU updates the U-TOC area (step T15) to terminate the recording operation normally. Where step T12 has determined that the user has not completed a dubbing operation, the CPU sets the address variable n to the next address number n+1 (a next data recording start address) and sets the data number N to the next data number N+1 (step T13). Then, it is determined whether the new set address n (=n+1) corresponds to a blank area (step T14).
If the address n (=n+1) does not correspond to a blank area, the U-TOC area is updated (step T15) and the recording operation is forcefully terminated (interruption of dubbing). Where the address n (=n+1) corresponds to a blank area, the execution returns to step T6, and the CPU starts (restart) recording of a new stored data N (=N+1) onto the disc when the remaining data quantity in the memory reaches the predetermined A.
FIG. 7 shows an example of a data arrangement of a U-TOC area in a MD. As illustrated in FIG. 7, on a top position of the U-TOC area, a header is provided. The header has a synchronizing pattern consisting of one-byte data each of which is 0 (zero) or 1 (one) identically. At a predetermined address, data including a first recorded music number (First TNO) 4, a last music number (Last TNO) 5, a U-TOC sector storage condition 6, a disc serial number 7, and a disc ID 8 is recorded. Furthermore, there is provided general data of storing segments 2 corresponding to a later-discussed control table 3 associated with all the recorded music numbers for storing various kinds of table pointers (P-DFA to P-TN0255).
Meanwhile, the controlling table 3 includes 255 rows of segments (01) to (FF). Each segment can record a start address showing a start point of a segment (physically continuing m track), an end address showing the segment end, segment mode information, and a link information indicating start and end addresses of a segment for connecting it to another segment.
That is, the U-TOC area, which is different from a normal music area, records information associated with the whole disc volume.
By the way, as stated above, such MDs having a small disc diameter are presently utilized mainly in portable units such as a headphone stereo. The portable units are subject to an impulsive force due to an abnormal vibration, falling, etc. due to the usage during the transportation thereof. Particularly, MD discs that are storage mediums have a data record surface sensitive to a scratch due to various reasons although they each are received in a cartridge like a 3.5 inch floppy disc.
That is, when recording onto a MD is carried out in a vibration-created environment, for example, a focus error or a tracking error may arise, causing record into an incorrect track (for example, in an adjacent track). Particularly, a wrong record in a track positioned inside the correct track on the disc may cause an undesirable data overweight to lose a correct recorded one.
As described above, the conventional information recording unit has the disadvantage that on recording, a disturbance like vibration may arises, for example, a focus error or a tracking error which may damage data recorded in an adjacent track.
Moreover, a wrong record in a track positioned inside the correct track on the disc may disadvantageously cause an undesirable data overwrite to lose a correct recorded one.